Secretary of State John Kerry said Tuesday that the several investigations into Hillary Clinton's private email system has significantly tied up the State Department over the last year, despite the more than $2 million Congress gave State to deal with it.

"We have more than 50 ... simultaneous investigations going on, and we have an unprecedented number of FOIA requests," Kerry told the Senate Foreign Relations Committee. "I have had to cannibalize bureaus to get people to go spend their time on these requests."

"I'm concerned about it because this is tying up international diplomats," he said.

Clinton's use of a private email has been a burden to State for nearly the last year, as the agency has had to slowly disseminate thousands of her private emails pursuant to a lawsuit. While Clinton claimed no classified information made its way onto her private server, more than 1,700 of those emails have since been classified since their release.

Kerry was pressed by Sen. Ron Johnson, R-Wis., about how much the effort has cost. Kerry said he didn't know, but said the few million Congress has provided isn't enough yet.

"I would have to look," Kerry said when asked to estimate the cost. "As I said to you, we have over 50 investigations, nine different committees involving hundreds of specific requests for literally hundreds of thousands of pages of documents."

"You allocated $2.4 million years '15 and '16 in order to help us respond to you, and we've been able to step up the level of our delivery as a result of that," he added. "But we're still greatly overburdened."

Johnson said the "mess" Clinton left at State has caused a real burden for the department in the years since she's left. "Secretary Clinton's actions have cost the federal government an awful lot of money, caused you an awful lot of headache," he said.

But Kerry insisted that it wasn't the mess Clinton left, but the dozens of investigations that her private email system prompted.

"It remains to be seen whether or not it's the 50 investigations by nine different committees that have created more heartburn," he said.